Contact pin for electric discharge tubes



y 11950 J. J. VAN DER SPEK 2,509,709

CONTACT PIN FOR ELECTRIC DISCHARGE TUBES Filed Dec. 6, 1947 .JOHANNES JACOBUS V. 05 E K INVE NTOR AGENT Patented May 30, 1950 CONTACT PIN FOR ELECTRIC DISCHARGE TUBES Johannes Jacobus van der Spek, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn, as

trustee Application December 6, 1947, Serial No. 790,030 In the Netherlands October 5, 1946 Section 1, Public Law 690, August 8, 1946 Patent expires October 5, 1966 2 Claims. (Cl. 250-275) This invention relates to contact members, more particularly contact pins for electric discharge tubes and incandescent lamps.

With the use of contact members, more particularly contact pins, the contact becomes unsatisfactory with age, due to which the transition resistance increases. This may often entail dimculties. Thus, for example, with discharge tubes used in receiving apparatus or amplifiers cracking noises are produced in the loudspeaker. Various attempts have already been made to eliminate this drawback. For instance, it is known to use silverplated contact surfaces. However, this solution is effective only for a short time, since in course of time the silver layer is scraped off, or diffuses into the sub-jacent material or is apt to turn black. To improve the silver layer it is known to render it more stable by thermal treatment and swaging or by precipitating the silver electrolytically in the form of a hard layer from certain solutions. Again it is known to coat the contacts with a ruthenium layer or to clean them by sandblasting. All these methods, however, are expensive or effective for a short time only, for example, the sandblasting operation.

According to the invention all of these difliculties can now be completely avoided in a surprisingly simple manner if, with contact members, more particularly contact pins for electric discharge tubes and incandescent lamps, at least the contact surface is polished. This yields the advantage that the surface has a beautiful lustrous appearance, whilst a very reliable contact is ensured which, as has been found, does not deteriorate with time. The material for the contacts preferably consists of ferrochromium, since this material is adapted to be sealed into glass. If, for examplaferrochromium contactpins sealed into the bottom of a discharge tube, oxidize during the sealing-in operation, it is possible for the end of these pins protruding from the tube to be polished chemically in a very simple conventional manner, for example by means of a bath containing perchloric acid and. acetic acid anhydride or another conventional bath. The polished surface apparently offers few points of attack to the air so that the ferrochromium pins remain bright for a long time.

Since the ferrochromium surface is comparatively hard it does not soon become damaged due to friction against the counter-contact.

It is known to polish small steel objects by chemical agency. These objects generally served as shafts or gudgeon pins for moving parts (engines), so that the problem of maintaining a bright surface in the air did not arise.

In order that the invention may be more clearly understood and readily carried into effect, it will now be described more fully with reference to the accompanying drawing, given by way of example, in which the sole figure represents part of a discharge tube comprising contact pins.

The bulb I of the tube is closed by a base 2, into which contact pins 3 are sealed.

After the lower part of the tube has been completely finished, the pins are chemically polished and the electrode system is welded to the other end of the pins, the bulb being secured to the bottom piece and the tube further finished. After the exhaust tube 4 has been melted oif, it may be surrounded by an envelope 5 comprising a location lug 6, care being taken, of course, that after polishing the pins are not subjected to strong heating. If measures are taken to prevent oxidation of the pins even during the sealing-in operation, use may be made of polished pins obtained, for example, by cutting from a polished wire. In this case it is possible to polish the wire mechanically, the gist of the invention being that the pins, inasmuch as they are in contact with the air and serve as contact members, should acquire a very smooth surface.

In the present embodiment use is made of contacts in the form of pins, but it will be obvious that the invention also applies to contacts of different shape, for example pins fixed in a cap or pins of plugs and the like. Furthermore it is not necessary for the pins to consist of ferrochromium. As an alternative they may also be made from nickel-iron, steel or similar hard material which is not subject to very strong oxidation.

What I claim is:

l. A contact pin for discharge tubes and the like, said pin being composed of a hard ferro alloy and having its contact surface polished by chemical action.

3 2. A contact pin for discharge tubes and the like, said pin being composed of a ferrochromium alloy and having its contact surface p01- ished by chemical action.

J OHANNES JACOBUS VAN DER SPEK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Number Name Date Scharfnagel Apr. 16, 1940 Hull Apr. 22, 1941 Reyling Jan. 12, 1943 Atlee Se t. 14, 1943 FOREIGN PATENTS Country Date Great Britain July 10, 1931 

